1. Field of the Invention
This invention relates to a device for detecting the center of a steering angle in a vehicle, and more particularly to an improved device for detecting the center of a steering angle, capable of eliminating a center error caused by the unsteadiness in steering in a short cycle, etc., and capable of accurately detecting an averaged center during running of the vehicle.
2. Description of the Prior Art
The center of a steering angle in a vehicle is very useful as the basic information for controlling the various components of the vehicle during running, and is widely used for the return control of a turn signal switch and so forth.
However, as has been well known, the steering of the vehicle has unsteadinesses in a short cycle. If a center is detected by constantly following such unsteadinesses, then there is presented a disadvantage that a component of error becomes excessively large, whereby the effective utilization of the detection signal is hampered in practice. Hence, heretofore, there have been proposed a number of methods of eliminating errors in detection due to the aforesaid unsteadinesses.
The invention disclosed in Japanese Patent Kokai (Laid-Open) No. 41270/82 has been well known as the preferable device for detecting the center of a steering angle of the prior art. According to this device, a center value detected from a steering angle sensor is temporarily stored in a temporary storage portion, the center value thus temporarily stored is successively renewed, only a renewed center value that continued for a predetermined distance during running of the vehicle is stored in a center storage portion, and the unsteadinesses in the steering in a short cycle other than the above are avoided being written into the center storage portion from the temporary storage portion to thereby be rejected, so that only the substantially effective center value can be taken out.
However, even the conventional device of the type described is disadvantageous in that an accurate center value for covering all of the various complicated running conditions of the vehicle cannot be obtained and that the aforesaid adoption or rejection of the center value only in dependence on the predetermined distance of running is unsatisfactory.